The present invention relates to USB devices and USB connecting systems using USB interfaces and, more particularly to a USB device or a USB connecting system capable of reducing power consumption of a host which supplies power thereto.
Recently, a universal serial bus (hereinafter referred to as USB) has been proposed as an external bus for interconnecting a personal computer (hereinafter referred to as host) and peripheral units. Since the USB is a xe2x80x9cserialxe2x80x9d bus, it has only four signal pins including those of a power supply line. It is thus possible to produce a thin cable and a small size connector for cost reduction, thus permitting more inexpensive peripheral units.
An utmost feature of the USB resides in that a plurality of different kinds of peripheral units can be supported by this single bus. In the conventional general-purpose interfaces such as keyboards, mouse devices, parallel ports and serial ports, the capability of connecting a plurality of peripheral units has been hardly considered. Recently, however, a USB has been proposed, which is capable of connecting and controlling up to 127 peripheral units at a time. In addition, up to 16 end points can be defined in a single peripheral unit. In other words, a single peripheral unit can be provided with up to 16 different functions.
However, once the USB device using the above USB interface is connected to a personal computer, power is supplied thereto from a host USB so long as it remains connected. That is, even when the USB device is not used, predetermined power is supplied from the USB device. To turn off the power supply for saving consumed power, the USB connector should be withdrawn from the host side USB.
Where the USB device is connected to the host internally of the same, the USB connector can not be withdrawn. Therefore, predetermined power is always supplied from the USB device irrespective of whether the USB device is used, thus resulting in wasteful power consumption.
Moreover, where the USB device is always connected to the host and used in a place distant therefrom, like the case when the USB device is not used, it is impossible to turn off the power supply.
The present invention was made in view of the above problems, and it has an object of providing a USB device or a USB connecting system using a USB interface capable of turning off the power supply from the host thereto without need of withdrawing the USB connector when stopping its operation.
According to an aspect of present invention, there is provided a USB device using a USB interface, comprising switching means for electrically on-off switching a 5-V power supply line for transmitting 5-V power supplied from an upper rank unit.
The USB device is connected by a connector to the upper rank unit either directly or via an HUB; and the switching means electrically on-off switches the 5-V power supply line led from the connector.
According to another aspect of the present invention, there is provided a USB device using a USB interface, comprising: input means for inputting settings from an operator; and control means for electrically connecting a 5-V power supply line for transmitting 5-V power supplied from an upper rank unit and then electrically connecting data lines in the USB device when an xe2x80x9conxe2x80x9d setting signal is provided from the input means, and electrically disconnecting the data lines and then electrically disconnecting the 5-V power supply line when an xe2x80x9coffxe2x80x9d setting signal is provided from the input means.
The USB device is connected by a connector to the upper rank unit either directly or via an HUB; and the control means controls the on-off switching of the 5-V power supply line and the data lines led from the connector.
According to other aspect of the present invention, there is provided a USB connecting system in which a USB device is connected by a USB interface to an upper rank unit either directly or via an HUB, wherein: the upper rank unit includes a driver for sending out a control signal for turning of f the power supply to the USB device; the USB device includes: power supply control means for on-off switching a 5-V power supply line for transmitting 5-V power supplied from the upper rank unit to the USB device and data lines for supplying data from the upper rank unit to the USB device side and transmitting data from the USB device side to the upper rank unit; and USB control means for transmitting a setting signal for disconnecting the 5-V power supply line and the data lines to the power supply control means when recognizing the control signal for turning off the power supply from the driver to the USB device; and power supply control means disconnects the data lines and then disconnects the 5-V power supply line in response to the setting signal from the USB control means for disconnecting the 5-V power supply line and the data lines.
The USB device includes input means for inputting settings from an operator; and the power supply control means connects the 5-V power supply line and then connects the data lines when a setting for connecting the upper rank unit and the USB device is provided form the input means.
According to still other aspect of the present invention, there is provided a USB device using a USB interface, comprising: a USB connector for connecting a USB device to a USB or HUB in a host; a serial interface engine serving as an interface interconnected by signal lines including a data line and a power supply line; and a switch connected to the power supply line for connecting and disconnecting the power supply line to the USB device.
According to further aspect of the present invention, there is provided a USB device using a USB interface, comprising: a USB connector for connecting a USB device to a USB or HUB in a host; a serial interface engine (SIE) serving as an interface interconnected by signal lines including a data line and a power supply line; and a switch for setting on/off state; a delay circuit provided between the USB connector and the serial interface engine for time-sequentially on-off switching the power supply line and the data line in accordance with the on/off state of the switch.
The delay circuit interconnects the USB connector and the serial interface engine in the order of the power supply line and the data line when the switch sets on state and disconnects the USB connector and the serial interface engine in the order of the data line and the power supply line when the switch sets off state.
The delay circuit interconnects the USB connector and the serial interface engine in the order of the power supply line and the data line after the lapse of a predetermined time since the power supply line connection when the switch sets the on state and disconnects the USB connector and the serial interface engine in the order of the data line and the power supply line after the lapse of a predetermined time since the power supply line disconnection when the switch sets the off state.
According to still further aspect of the present invention, there is provided a USB device using a USB interface, comprising: a USB connector for connecting a USB device to a USB or HUB in a host; a serial interface engine serving as an interface interconnected by signal lines including a data line and a power supply line; and a switch for setting on/off state; a USB control unit for recognizing a signal indicative of xe2x80x9cpower offxe2x80x9d transmitted from the host side through control transfer and transmitting a xe2x80x9cpower offxe2x80x9d setting signal; a power supply control unit provided between the USB connector and the serial interface engine for time-sequentially on-off switching the power supply line and the data line in accordance with the on/off state of the switch and the xe2x80x9cpower offxe2x80x9d setting signal from the USB control unit.
The power supply control unit interconnects the USB connector and the serial interface engine in the order of the power supply line and the data line after the lapse of a predetermined time since the power supply line connection when the switch sets the on state and disconnects the USB connector and the serial interface engine in the order of the data line and the power supply line after the lapse of a predetermined time since the power supply line disconnection when the switch sets the off state or the xe2x80x9cpower offxe2x80x9d setting signal from the USB control unit.
The power supply line is provided with 5-V.
According to further aspect of the present invention, there is provided a power supply control method of a USB device using a USB interface having signal lines including a data line and a power supply line, wherein the power supply line and the data line are time-sequentially on-off switched in accordance with an on/off instruction.